For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.
Draw blood immediately before next scheduled dose (trough specimen).
Centrifuge within 2 hours of collection.
Toxicity effects other than acute hypersensitivity infusion reactions have not been described nor correlated with infliximab concentrations.
During the initial induction phase of treatment (weeks 0, 2 and 6), steady-state has not been achieved and concentrations of infliximab may vary significantly between infusions.
Therapeutic concentrations of infliximab may vary according to the disease (eg, Crohn disease vs ulcerative colitis vs rheumatoid arthritis).
Samples containing more than 12.5 ng/mL biotin (vitamin B7) may interfere (in the form of depressed signal) with INXAB / Infliximab Antibodies, Serum.
For antibodies-to-infliximab (ATI), pediatric and adult reference ranges were validated, and the presence of an ATI is established as greater than or equal to 50 U/mL by our bridging electrochemiluminescent/acid dissociation method.
The presence of endogenous infliximab is a recognized interference in most ATI methods. This assay includes an acid dissociation step, which partially mitigates this interference. Tolerance up to 12.5 mcg/mL infliximab has been documented, although this is also determined by the titer of the ATI present in the patient sample
INFX: Monday, Wednesday, Thursday
INXAB: Monday, Wednesday, Friday
INFXR, INFX: Selective Reaction Monitoring Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
INXAB: Electrochemiluminescent Bridging Immunoassay with Acid Dissociation
INFLIXIMAB ANTIBODIES: Absence of antibodies to infliximab (ATI) is defined as <50 U/mL
Presence of ATI is reported as positive when concentrations are > or =50 U/mL